The present invention relates to a method of producing a color filter for a solid-state imaging device, for example, a CCD (Charged-Coupled Device), and a liquid crystal display device.
Recently, in the production of a color filter on a light receiving sensor portion of a color display solid-state imaging device, a pigment containing photosensitive resin method called a color resist method has come to be adopted in place of a dyeing method.
The color resist method (pigment containing photosensitive resin method) has a large merit from the viewpoint of its production because it does not require a dyeing step.
The above-described color resist method, however, has a disadvantage in the case where a fine color filter to be used, for example, for a solid-state imaging device is formed of filter elements of red (R), green (G), and blue (B) colors. That is to say, in this case, since an exposure amount necessary for patterning these color filter elements becomes significantly large, it is difficult to pattern these filter elements with a high accuracy.
The sensitivity of a color resist is naturally low because the color resist contains a pigment in a large amount. To cope with an inconvenience caused by the low sensitivity of the color resist, a negative resist having a higher sensitivity has been used as the color resist.
For example, as a resist for forming filter elements of red, green and blue (RGB), a pigment dispersion type acrylic negative resist formed by adding a multi-functional acrylic monomer, a photo-polymerization initiator, and a pigment into a binder resin has been generally known and widely available. This resist, if it contains no pigment, has a sensitivity being as large as 100 times or more that of a novolak positive resist (formed by adding a naphthoquinone diazide based a photosensitizer into a novolak resin) which has been applied to fine processing.
However, if a fine color filter for a solid-state imaging device is formed by using the above-described pigment dispersion type acrylic negative resist in which a pigment is dispersed, there may occur a problem that the image quality of the solid-state imaging device is significantly degraded because of the insufficient resolution of the resist, the inversely tapered edge shape of the obtained resist pattern, and color mixing and uneven sensitivity between pixels caused by influence of a residual pigment after development.
Accordingly, it is expected to provide a method of producing a color filter composed of filter elements of RGB and used for a solid-state imaging device, which color filter is capable of improving the resolution of the solid-state imaging device.